Windows RAID offers several advantages. You can create arrays from within Window Drive manager so there's no BIOS to configure. It's also more flexible with mirrors, allowing you to create them from existing volumes containing data, as well as delete either half of a mirror with the other remaining intact. You can mirror individual partitions, including partitions from different drives onto a single drive.

The disadvantages are that other operating systems, such as the Linux used on repair discs, can't see Windows software RAID partitions which use Microsoft's dynamic disk technology. Also, maintenance performed by Windows when it feels it's needed, which can occur any time there's a configuration change, hurts performance while in progress. Restoring mirrors isn't as dead simple as it is with a hardware solution either.

Though you'll see a lot of talk about hardware RAID being faster, this discussion predates modern CPUs which can easily handle the overhead. Windows RAID is actually quite fast.